OK,
With bleach, you look for the % on the label. Regular bleach is 5.25%, ultra is 6%. But now there are some "economy" types that are 3%--ultimately they cost more for the actual bleach than 6%.

Chlorox now has a added whitening agent which may or may not be good for pools--the jury's still out. In the meantime, generic bleach is better.

There are 3 test kits that will serve your purposes. All are basically the same and it doesn't matter really which you get. All use a chlorine test called FAS-DPD, which is NOT the same as the chlorine test called DPD.

1) Taylor brand K-2006 or K-2006C from Taylortechnologies.com
Taylor makes the chems that most of the better kits use. The C has more of each chem, but costs more.

2) Leslie's Pools Online (not their retail stores)--their FAS-DPD Chlorine Service Test Kit. Leslies test kits are ALL re-branded Taylor kits.

3) Troublefreepools.com. I don't know a lot about these kits other than they are similar in concept to the kits that used to be sold at our sister site Poolsolutions.com--the PS-234 (no longer available) What I do know about TFP kits is they use FAS-DPD for chlorine testing and have a complete suite of tests as the others do.

In a pinch, your local Wal-Mart may have an HTH 5-way Pool Test Kit that uses drop-testing, not strips. This will only measure chlorine via the OTO test to 5ppm, but diluting pool water with distilled water can extend the range. It's a lot cheaper but much more limited. Still, it's a bargain at $12 to $15 and far better than most of the other kits out there--and better than strips.

Search our site for the "Best Guess Table" -- it's stickied. It will show you the FULL range of CYA to FC levels. For a CYA of 100ppm, FC should normally be no lower than 8 and no higher than 15ppm. To shock, raise FC to 25ppm.

Dilution (such as rain) will help lower your CYA, but if you replace 25% of your water, you CYA will STILL be 75ppm.